JP2002362983A - Dry gel composite material and heat-insulating material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry gel composite material capable of being produced with a good production efficiency and having sufficient strength, and a heat insulating material using the same. SOLUTION: The dry gel composite material contains hydrophobic dried gel particles having a density of 100 to 400 kg/m<3> and a first reinforcing material integrated with the dried gel particles, and the dry gel particles are stuck with one another through the first reinforcing material mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite used for a heat insulating material, a sound absorbing material, a catalyst carrier, and the like, and a heat insulating material comprising the composite.

[0002]

2. Description of the Related Art When a dried gel is used as a heat insulating material, a sound absorbing material, a catalyst carrier or the like, a dried gel having a large surface area and a low density is generally preferred. Further, in consideration of the incorporation into a device, it is preferable to be able to mold into various forms of blocks. Further, since the low-density dried gel has low strength, it is necessary to improve the strength. However, the wet gel, which is a precursor, shrinks during drying due to the capillary force in the gel pores, so that the density increases, cracks easily occur, and flakes tend to occur. For this reason, it is difficult to obtain a dried gel block.

[0003] On the other hand, there are mainly two methods known as methods for obtaining a block-shaped dry gel while suppressing shrinkage. The first method is a supercritical drying method.
Since the drying is performed at a pressure and temperature higher than the critical point of the solvent, a gas-liquid interface is not formed during drying. Therefore, drying can be performed without causing shrinkage due to capillary force, and a block body can be obtained without cracking. This method was developed by Kistler as a method using supercritical drying of alcohol (Journal of Physical Chemistry, Vol. 36, pp. 52-64, 1932), and later Hunt et al. Changed to supercritical drying using carbon dioxide. (US Pat. No. 4,610,863). However, in this method, although a block without cracks is obtained, a dried gel having the necessary strength at the time of handling cannot be obtained.

Next, as a second method, a method of drying by reducing the capillary force by hydrophobizing the gel surface (US Pat. No. 3,015,645, Journal
Obnon-Crystalline Solid, 186 volumes, 10
Pp. 4-112, 1995). According to this method, the gel shrinks as drying proceeds, and when drying is completed, the gel is restored to its original size and a low-density gel is obtained.
However, cracks are likely to occur due to stress caused by shrinkage during the progress of drying. Further, similarly to supercritical drying, improvement in strength is not realized.

As described above, since it is difficult to secure the strength of the dried gel itself, a method of increasing the strength as a block body by using a reinforcing material has been studied. The method is mainly classified into the following two methods.
The first is a method in which a fibrous body, a fiber cloth or a non-woven fabric is used as a reinforcing material, and at the time of forming a wet gel, the reinforcing material is compounded to form a composite block, which is dried (Japanese Patent Laid-Open No. 6-182222). No.). A second method is a method in which a dried gel particle is molded into a mixture of a reinforcing material such as a fibrous body, a gel, and a binder to obtain a composite block (Japanese Patent Application Laid-Open No. 10-504793).

[0006]

As described above, when a reinforcing material is used to secure the strength, a method of forming a wet gel in the form of a block by making the reinforcing material coexist at the time of gel formation and drying the gel is used. However, although the strength can be ensured, there is a problem that a long time is required for producing a block-shaped wet gel because it takes time for solvent replacement and the like. On the other hand, a method of first producing a hydrophobized dried gel particle and molding it with a reinforcing material such as a fiber and a binder is efficient because the gel particle can be manufactured in a short time, There was a problem that the strength obtained was not sufficient. Therefore, an object of the present invention is to provide a dry gel composite having good strength and sufficient strength, and a heat insulating material using the same.

[0007]

The present invention comprises hydrophobic dry gel particles and a first reinforcing material integrated with the dry gel particles, wherein the dry gel particles adhere to each other via the reinforcing material. And a dry gel composite. It is effective that the dried gel composite has a protective film on its surface. Further, the dried gel composite includes a second reinforcing material that is not integrated with the dried gel particles,
It is effective that the second reinforcement is bonded to the first reinforcement. Further, the density of the hydrophobic dry gel particles is preferably 100 to 400 kg / m ³ . Further, the present invention relates to a heat insulating material comprising the dried gel composite.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The dry gel composite of the present invention and a method for producing the same will be described below. FIG. 1 is a partially enlarged view schematically showing the structure of the dried gel composite of the present invention.
The feature of the dry gel composite of the present invention is that, as shown in FIG.
Are bonded together at the bonding points 4 to form a composite. The first reinforcing members 3 are in the first
If the reinforcing material 3 has a low melting point, or if the first reinforcing material 3 contains a component having a low melting point, it can be melted and bonded (fused), and bonded using an adhesive. You can also.

Conventionally, when a reinforcing material is added to form dry gel particles, a discrete reinforcing material and dry gel particles are mixed and formed. However, it is difficult to secure the strength as a composite because the adhesiveness between the dried gel particles or the adhesiveness between the dried gel particles and the reinforcing material is poor. On the other hand, in the present invention, the first reinforcing material and the dried gel particles are integrated, and even if the dried gel particles do not adhere to each other or the dried gel particles and the first reinforcing material do not adhere to each other, the adhesiveness is improved. By bonding good first reinforcing members 3 to each other, an effect of increasing the strength as a composite can be obtained. Of course, the dried gel particles may be bonded to each other, or the dried gel particles may be bonded to the first reinforcing material.

The dry gel particles in which the first reinforcing material used in the present invention is integrated are added with a reinforcing material when forming a wet gel by a so-called sol-gel method, and are integrated with the first reinforcing material. It is obtained by obtaining a wet gel, which is then dried to remove the solvent. The gelation of the gel can be performed mechanically at the time of formation, after formation, or after drying of the wet gel. From the viewpoint of handling, the particle size of the obtained dry gel particles is from about 10 μm to about 5 mm. preferable.

As a raw material of the gel, a metal compound generally used in a sol-gel method can be used.
For example, oxides such as silicon, aluminum, zirconium, and titanium can be used. Among them, silicon oxide is preferred from the viewpoint of easy availability. Examples of silicon oxides include silicon alkoxides such as tetramethoxysilane and oligomers thereof, colloidal silica, water glass, and the like, and a silicic acid aqueous solution obtained from water glass by electrodialysis is preferably used. Further, as other gel raw materials, phenols-formaldehyde, melamine-
Organic compounds such as formaldehyde and polyol-isocyanate can also be used.

The wet gel obtained from the above-mentioned metal compound is given hydrophobicity by performing a hydrophobic treatment. The hydrophobic treatment may be performed by immersing the wet gel in a non-aqueous solvent containing a hydrophobic agent. As the hydrophobizing agent, a silylating agent is preferred because of its high reactivity, and examples thereof include disilazane, chlorosilane, alkylsilanol, and alkoxysilane. Specifically, chlorosilane compounds such as trimethylchlorosilane, methyltrichlorosilane, and dimethyldichlorosilane, silazane compounds such as hexamethyldisilazane, methoxytrimethylsilane, ethoxytrimethylsilane, dimethoxydimethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane, and the like A silylating agent represented by a silanol compound such as an alkoxysilane compound and trimethylsilanol and triethylsilanol is preferably used.

As a result, the introduction of an alkylsilyl group such as a trimethylsilyl group to the surface of the gel promotes hydrophobicization. Also, if a fluorinated silylating agent is used as the hydrophobizing agent, the hydrophobicity becomes stronger and is very effective. For example, chlorosilanes having a perfluorofluoroalkyl group can be suitably used.

Further, as the first reinforcing material used in the present invention, there are a fiber and the like in addition to the honeycomb structure. Examples of the fibers include organic fibers such as glass fibers or mineral fibers, synthetic fibers such as polyester fibers, aramid fibers, and nylon fibers, and natural fibers. Further, a fiber aggregate such as a fiber cloth or a nonwoven fabric made of these fibers can also be used. Further, polyurethane-based, polyester-based, vinyl chloride-based, polyolefin-based, polystyrene-based, and silicone-based foams can also be used.

When a gel is prepared by adding the above-mentioned first reinforcing material in order to prepare a dried gel, the reinforcing material such as fiber or foam is crushed or cut to a desired particle size in advance and added. You can also. In addition, it is preferable that the reinforcing material itself has strong adhesiveness. Among the above, the low melting point organic fiber or the organic fiber or glass fiber coated with the low melting point material, the foam, etc. can be bonded by fusion. Is preferable.

In the present invention, it is also possible to bond the first reinforcing members to each other with an adhesive. In this case, in addition to an organic solvent-based adhesive, a water-based or water-based emulsion-based adhesive, And a hot-melt adhesive containing no organic solvent can also be used. Above all, when the gel is hydrophobized, the organic solvent easily penetrates into the gel, and the gel shrinks easily when the organic solvent is subsequently dried, so that an aqueous or aqueous emulsion adhesive, It is preferable to use a solventless adhesive such as a hot melt type. However, if the viscosity of the solvent-based adhesive is high, it does not enter the pores of the dried gel, so that the pores do not shrink and can be used.

The water-based or water-based emulsion-based adhesive can be applied by spraying if the viscosity is low. Also, as a form, solid adhesive such as powder,
By mixing uniformly with the dried gel particles, a good adhesive effect can be exhibited. For example, powders of thermoplastic polyethylene, polypropylene, vinyl acetate and the like are used. Further, a thermosetting resin powder, such as a phenol resin, which is cured by the presence of heat or acid is used.

In the present invention, the dried gel composite preferably has a protective film on its surface. The protective film is
Since it is formed by bonding with the first reinforcing material integrated with the dried gel particles, it does not easily peel off, increases the surface strength, and has an effect of preventing the dried gel particles from falling off due to handling. . The protective film can be made of various organic polymer materials or inorganic polymer materials. When a thermoplastic organic polymer material is used to form the protective film, a thermoplastic resin is used as the first reinforcing material, so that a sheet made of the thermoplastic resin is melted in the reinforcing material layer. It is easy to wear. Alternatively, a protective film can be formed by applying a thermoplastic resin or thermosetting resin precursor as a solution of an organic solvent or an aqueous emulsion to the surface of the composite and curing it by heating, irradiation of ultraviolet light, penetration of water vapor, etc. It is.

Further, it is also possible to form a protective film by attaching a sheet made of an organic polymer such as a silicon resin to the surface of the composite using various adhesives. The application of the above-mentioned organic solvent or aqueous emulsion can be sprayed through a nozzle when the viscosity is low. In particular, when the dried gel is hydrophobic, it is easy for the organic solvent to enter the gel, and the gel shrinks when the organic solvent dries, so that an aqueous solution of a water-soluble polymer or a water-insoluble polymer It is preferred to use an aqueous emulsion of

Further, in the present invention, in addition to the first reinforcing material integrated with the dried gel particles, a second reinforcing material is added, and the newly added second reinforcing material is integrated with the dried gel. It is preferable to adopt a configuration in which it is bonded to the first reinforcing material. In particular, it is preferable that the second reinforcing member is bonded to many integrated first reinforcing members. This has the effect of further improving the strength of the composite. When a new second reinforcing material is added, when a protective film is formed on the surface, the new second reinforcing material is adhered to the protective film on the composite surface to form a protective film. The effect of increasing the strength of the film is obtained. As the second reinforcing material, those described above with respect to the first reinforcing material can be used. The second reinforcing member may have a relatively large size, and a honeycomb structure or various foams may be used as they are.

When the dry gel composite according to the present invention obtained as described above is used particularly as a heat insulating material, the surface of the dry gel composite preferably has a buffering action.
It is effective to form a buffer layer on the surface of the dried gel composite. In that case, even if the shape of the dry gel composite does not match the shape of the box or the part incorporated in the device, the buffer material layer on the surface of the dry gel layer is deformed, so that there is no gap in the built-in part It can be installed. As a result, an air layer having poor heat insulating properties is prevented from being formed in the gaps, and a reduction in heat insulating performance is suppressed.

In this case, as a material constituting the buffer layer,
Fiber aggregates and various foams having open cells and heat insulation are preferably used. Specific examples include woven, non-woven, and mats of the above various fibers. Further, the above-mentioned foams having open cells are preferably used. Among these, glass wool is preferable because it is easily available. Hereinafter, the present invention will be described based on specific examples, but the present invention is not limited thereto.

[0023]

Example 1 In this example, a dry gel composite was formed using silica dry gel particles integrated with glass fibers. (1) Production of Silica Dry Gel Particles Integrated with Glass Fiber Glass wool (Asahi Fiberglass) was added to 100 parts by weight of a mixture of tetramethoxysilane, ethanol and 0.1N ammonia water (1: 3: 4 (molar ratio)). 5 parts by weight of glassron wool (manufactured by Co., Ltd.) cut into about 5 mm or less were added and stirred to promote gelation. The formed wet gel was aged at 25 ° C. for 3 days, ethanol was added thereto, and the mixture was pulverized by a stirrer into particles of about 2 to 3 mm or less.

Next, the above-mentioned wet gel was used for 5 times the gel volume.
The operation of immersing in ethanol equivalent to the amount of
Perform a total of 3 times by replacing with fresh ethanol
The water inside was replaced with ethanol. Similarly, wet gel
The solvent in was replaced with ethanol and hexane. That
After that, trimethylchlorosiloxane equivalent to 5 times the gel volume
45 g of the wet gel in a 10% by weight solution of orchid in hexane.
A hydrophobizing treatment was performed by immersion at 1 ° C. for 1 day. Get
Hexane in the hydrophobized wet gel
After substituting with liquefied carbon dioxide in
Release the atmospheric pressure of 12 Mpa while maintaining
To dry. To the obtained hydrophobized dry gel particles
Is embedded with cut glass wool, and both
It was confirmed that they were united. The density of the gel particles is
230kg / m ^ThreeMet.

(2) Formation of Dry Gel Composite 100 parts by weight of the dry gel fine particles obtained by the above (1), in which glass wool is integrated, ethylene-vinyl acetate copolymer (F16180 manufactured by Sumitomo Seika Co., Ltd.) -N) was mixed and stirred at 20 parts by weight.
The molding was performed by applying a pressure of g / cm ² .

Further, a 5% aqueous solution of polyvinyl alcohol was applied to the surface of the obtained molded body, and dried to form a protective film. Thereby, the dried gel composite 1 of the present invention was obtained. The obtained composite was 10 cm × 10 cm × 1.
It has a block shape of 2 cm, a density of about 330 kg / m ³ and a thermal conductivity of 0.020 W / mK at an average temperature of 24 ° C.
Met. In addition, gel was not lost even when carried by hand, and it was confirmed that the gel had strength for normal handling.

Example 2 In this example, a dry gel composite was formed by adding a new second reinforcing material that was not integrated with the dry gel. Using silica dry gel particles integrated with glass fiber, when forming a dry gel composite,
A dried gel composite 2 of the present invention was formed in the same manner as in Example 1 except that 5 parts by weight of glass wool (Glass Ron wool manufactured by Asahi Fiber Glass Co., Ltd.) cut to about 1 cm was added.

The obtained composite was 10 cm × 10 cm ×
1.2cm block shape, density about 330kg / m ³
The thermal conductivity is 0.0205 W at an average temperature of 24 ° C.
/ MK. It was confirmed that this composite also had a strength that would not hinder handling. In addition, the dried gel composites 1 and 2 were put into 10 cm × 1 cm × 1.2 c
By cutting the test piece into a rod shape of m and pressing the two rod-shaped test pieces crossing each other at the center, the rigidity of the two test pieces was compared. As a result, the composite 1 obtained in Example 1 was bent. It was confirmed that the strength of the composite 2 including the second reinforcing material was increased.

Example 3 In this example, a thermoplastic resin powder was used as a binder for bonding a reinforcing material. A dry gel composite of the present invention was prepared in the same manner as in Example 1 except that 20 parts by weight of polypropylene fine particles (FLOWBRENE manufactured by Sumitomo Chemical Co., Ltd.) was used instead of the water-soluble cellulose ether, and the molding temperature was 160 ° C. Body 3 was produced. The obtained composite was a block of 10 cm × 10 cm × 1.2 cm, the density was about 260 kg / m ³ and the thermal conductivity was an average temperature of 2
It was 0.022 W / mK at 4 ° C. Further, it was confirmed that the gel was not damaged even when carried by hand, and that the gel had strength for normal handling.

[0030]

The dried gel composite of the present invention is characterized in that the reinforcing material is integrated with the dried gel fine particles and the reinforcing materials are adhered to each other, which has the effect of having excellent strength. Play. Further, the dry gel composite of the present invention having a protective layer on the surface has an effect of having sufficient surface strength for handling. Furthermore, when the dry gel composite of the present invention has a configuration including the second reinforcing material that is not integrated with the dry gel particles, the effect of further improving the strength is exhibited. In addition, the heat insulating material made of the dried gel composite of the present invention has the effects of not requiring much time for production, realizing sufficient strength, and realizing excellent heat insulating performance.

[Brief description of the drawings]

FIG. 1 is a partially enlarged view schematically showing the structure of a dried gel composite of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dry gel composite 2 Dry gel particle 3 First reinforcement 4 Adhesion point of 1st reinforcement

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2E001 DD01 DF04 GA01 GA03 GA84 HB01 JA21 JA22 JC08 JD01 JD04 JD05 4G019 CA03 CB03 CC02

Claims (5)

[Claims] 1. A dry gel particle comprising: a hydrophobic dry gel particle; and a first reinforcing material integrated with the dry gel particle, wherein the dry gel particles are bonded to each other via the reinforcing material. Dry gel complex. 2. The dry gel composite according to claim 1, having a protective film on the surface. 3. The method according to claim 1, further comprising a second reinforcing material that is not integrated with the dried gel particles, wherein the second reinforcing material is bonded to the first reinforcing material. Dry gel complex. 4. The density of the hydrophobic dry gel particles is 1
00~400kg / m ³ a is claim 1 dry gel composite according. 5. A heat insulating material comprising the dry gel composite according to claim 1.